1. Field of the Invention
The present invention relates generally to a cable television (CATV) decoder interface. More particularly, it relates to such an interface for connecting the cable television decoder to a television accessory, such as a video cassette recorder (VCR). Most especially, it relates to such an interface which maintains full functionality of the television accessory while connected to the decoder.
2. Description of the Prior Art
Cable television decoders typically operate by requiring a television set and a VCR connected to the decoder to be set to a predetermined channel, such as channel 2, 3 or 4, and all channel selection is accomplished by the decoder. This presents problems for unattended recording, in that not all of the advanced features available on state-of-the-art VCRs can be used while the VCR is under control of the decoder.
Two Zenith Electronics Corporation technical papers disclose systems which attempt to deal with this problem. Merrell, "Tac-Timer," 1986 NCTA Technical Papers, pp. 203-206, discloses a smart remote controller to solve the unattended programming problem when a cable decoder precedes a VCR. In lieu of programming the VCR, the smart remote controller is programmed to turn on a VCR at specific times to record desired programs. However, this remote controller does not coordinate channel selection for such devices as television schedule systems, such as disclosed in my U.S. Pat. No. 4,706,121, issued Nov. 10, 1987, nor does it support unique features of more advanced VCRs. For example, this controller does not support on-screen VCR programming, even if that feature is otherwise available on a VCR. The controller does not include any capability for conveying information about a channel selected on the cable decoder unit to a television schedule system or a VCR in any useful way.
Long, "The VCR Interface," 1986 NCTA Technical Papers, pp. 197-202, discloses two solutions for the unattended programming problem when a cable decoder precedes a VCR. The first of these is a VCR baseband decoder, also called BASE-TAC, and currently marketed by Zenith as MultiPort or MP. MPs allow the core functions (descrambling and addressing) of a cable decoder to be added to Tvs and VCRs. The decoder accepts the baseband output of the TV or VCR tuner, eliminating the need for a separate decoder tuner and attendant need to coordinate two tuners. This method is effective for supporting television schedule systems and allows full functionality of advanced VCR features. However, the MP alternative requires new TV or VCR equipment and is not compatible with the existing installed base of cable decoders. This method has not been well-received at this time. The second is the VCR Interface, which uses RF switching and a centralized approach for all TVs and VCRs in the home. It descrambles incoming CATV channels and, after modulation, combines them back onto the CATV cable at unused upper channels. The result is that any TV set on the cable can receive premium channels without a separate decoder. This method eliminates the need for redundant decoders at every TV set or VCR. As described, the system was conceived for only one premium channel. To support a television schedule system, all premium channels must be descrambled together and be available simultaneously. If not, it would be necessary to provide a way of tuning the centralized descrambler from any TV set or VCR attached to the cable. Such a scheme would be awkward when more than one TV or VCR competes for control of the single descrambler. The VCR interface may be implemented using retrofitted decoders, but the overall cost may be prohibitive for the average home.
A somewhat similar system for use with the German television networks is described in Sommerhauser, "Video Programm System: Flexibel programmieren mit VPS," Funkschau, No. 25, Dec. 1985, pp. 47-51.
Other prior art relating to CATV, its decoders, and programmable remote devices includes West German Published application no. 2,338,380, published Feb. 13, 1975; U.K. Pat. No. 1,554,411, published Oct. 17, 1979; U.S. Pat. No. 4,375,651, issued Mar. 1, 1983 to Templin et al.; U.S. Pat. No. 4,394,691, issued Jul. 19, 1983 to Amano et al; U.S. Pat. No. 4,802,114, issued Jan. 31, 1989 to Sogame. While the prior art relating to cable decoder interfaces and similar devices is a welldeveloped one, a need remains for further development of such devices. None of the existing interfaces both provides a complete solution to the problem of unattended recording and is compatible with already installed equipment.